1. Field of the Invention
The present invention relates to a process and an apparatus for producing gas hydrate pellets by compression-molding a gas hydrate, and more specifically relates to a process and an apparatus for producing gas hydrate pellets, which are capable of producing at low cost gas hydrate pellets having an excellent storability.
2. Description of Related Art
In these days, as safe and economical means for transporting and storing a natural gas or the like (hereinafter, called a “raw-material gas”), a method using a gas hydrate obtained by hydrating the raw-material gas into a solid hydrate has been in the limelight. A gas hydrate is generally generated by reacting a raw-material gas and water under low temperature, high pressure conditions. The gas hydrate thus generated is in the form of a slurry containing 40 to 60% by weight of water. For this reason, a technique for storing the gas hydrate has been employed in which the gas hydrate content is increased to approximately 90% by weight by dewatering, regeneration, or the like, and then the gas hydrate is compression-molded at atmospheric pressure into a product (hereinafter, called “pellets”) in an almond form, a lens form, a spherical form, or an indeterminate form (for example, refer to Patent Document 1). This technique has a problem in that a large part of the gas hydrate pellets, which are stored at a temperature of −20° C. and atmospheric pressure, is decomposed in a short time period. For solving such a problem, Patent Document 2 proposes the following method. Specifically, a gas hydrate having such a particle size that the decomposition thereof is suppressed by the self-preservation effect is separated to be stored through classification. The gas hydrate that is removed through the classification is decomposed and the gas hydrate is regenerated from the result of the decomposition.
However, such a method requires facilities for the classification and the rehydration of gases, thus leading to an increase in the production cost for gas hydrate pellets.    Patent Document 1: Japanese patent application Kokai publication No. 2002-220353    Patent Document 2: Japanese patent application Kokai publication No. 2003-287199